Dual‐Channel SPR Sensor Based on an Elliptical‐Core Double‐Hollow Fiber With Subwavelength Gratings

ABSTRACT A dual‐channel surface plasmon resonance (SPR) sensor is proposed, based on an elliptical‐core double‐hollow fiber that integrates subwavelength gratings (SWGs). By etching a microstructure with subwavelength periodicity on the outer wall of the fiber and depositing a metal layer, the coupling efficiency between the guided light and the metal interface can be significantly enhanced. We first demonstrate a subwavelength SPR sensor employing single‐mode fiber and photonic crystal fiber, each showing several‐fold improvement in performance. Furthermore, by extending this design to a dual‐channel SPR sensor, simulations indicate that the refractive index (RI) sensitivity can exceed 15 000 nm/RIU in dual‐channel detection, while also enabling temperature measurement with a temperature sensitivity of approximately −5 nm/°C. Compared with traditional single‐channel fiber SPR sensors, the proposed structure not only offers higher sensitivity but also supports multi‐parameter detection. Owing to its unique design, the design effectively reduces coupling between the two channels, thereby maintaining low channel crosstalk even under high‐sensitivity conditions. This study introduces an innovative design for high‐sensitivity, multi‐parameter SPR fiber sensors. Broadening the application of SWGs in fiber sensing.